1. Field of the Invention
The present invention relates to a tray holding apparatus for supplying trays that have been held or for holding trays recovered.
2. Description of the Related Art
Conventionally, some kinds of parts are mounted on to various electronic components such as liquid crystal panels by a mounting apparatus. For example, a mounting apparatus sequentially mounts semiconductor chips, flexible substrates, etc. onto liquid crystal panels.
This type of mounting apparatus includes, for example: a unit for supplying liquid crystal panels; a unit for supplying semiconductor chips to a unit that mounts the semiconductor chips; a unit for mounting the semiconductor chips on the liquid crystal panels; a unit for supplying flexible substrates to a unit that mounts the flexible substrates; a unit for mounting the flexible substrates on the liquid crystal panels on which the semiconductors have been mounted; and a unit for recovering liquid crystal panels on which the various components have been mounted. The liquid crystal panels are subject to various processes while being sequentially transferred to the unit for mounting semiconductor chips, the unit for mounting flexible substrates, and the unit for recovering the panels.
In each of the units, a group of components used in the unit is accommodated in each tray. For example, in the unit for supplying liquid crystal panels, each tray accommodates a group of liquid crystal panels that have not yet been processed, and each of the liquid crystal panels is taken out from this tray and undergoes processing. When the tray has become empty of the components, another tray accommodating similar components is prepared.
There have been proposed apparatuses that hold a plurality of trays and supply the trays one after another. Trays used in such tray supply apparatuses are arranged in a stack. The apparatus supports the lowermost tray in a stack of trays, thereby holding all the stacked trays, or allows the lowermost tray to fall, thereby supplying each tray in series.
However, trays have a recessed cross-section due to their upward projecting periphery (i.e., outer boundary or edges). Accordingly, a tray may fit into the tray lying immediately below it. This may result in such failure of supply that the lowermost tray cannot be separated from the tray lying immediately above it.
In order to avoid such a situation, this type of apparatus includes a separation unit for separating the lowermost tray. This type of separation unit includes separation members in the form of a pawl. The separation members grasp the lowermost tray and separate it downward. Such a technology has been disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2005-239298.
However, the apparatus disclosed in this publication allows the lowermost tray to fall downward. This may result in a disadvantage, such as components (e.g., electronic components) accommodated in the tray scattering while falling to be supplied.
Additionally, in this publication, the apparatus that allows the lowermost tray to fall downward has been proposed, but no design for the recovery of empty trays (if required), has been disclosed.